1. Field of the Invention
The present invention relates to an transmissivetype photo-interruptor for detecting the presence or absence and the moving direction and moving distance of an object to be detected which has slits, and more particularly to an trans-missivetype photo-interruptor free from cross talk which is utilized for detection of the moving direction and moving distance of, for example, a mouse adapted to control the cursor or the like on the display of information apparatus.
2. Description of the Prior Art
In a conventional trans-missivetype photo-interruptor utilized for detecting the moving direction and moving distance of the mouse adapted to control the cursor or the like on the display of information apparatus, a single light emitting element 1 bonded to one lead terminal 2a is connected to the other lead terminal 2b by a gold wire 3 and molded with transparent resin to form a light emitting side transparent resin block 4 (a primary mold) as shown in FIG. 3, two light receiving elements (photo detector element) 5a and 5b both bonded to one lead terminal 2c are respectively connected to the other two lead terminals 2d and 2e by gold wires 3 and molded with transparent resin to form a light receiving side transparent resin block 6 (a primary block) as shown in FIG. 4, the light emitting side transparent resin block 4 and the light receiving side transparent resin block 6 are disposed to oppose each other through a predetermined distance as shown in FIGS. 1 and 2, and these transparent resin blocks 4 and 6 are integrally molded with opaque resin excepting their light pass windows 4a and 6a to form an opaque resin sheath 8 (a secondary mold).
When utilizing the trans-missivetype photo-interruptor for the mouse, an object 7 to be detected having slits S which is rotated as the ball of the mouse rotates passes through a gap between the light emitting element 1 and the light receiving elements 5a and 5b as shown in FIGS. 5 and 6, so that mutually dephased output signals as shown in FIG. 7 can be produced from the light receiving elements 5a and 5b to permit detection of the moving direction and moving distance of the mouse.
As the object 7 of detection, a thin member made of metal has hitherto been used having a thickness T2 which is sufficiently smaller than a width W of the slit S as shown in FIG. 5 but recently, from the standpoint of weight reduction and cost reduction, a thick member made of resin has been used as the object 7 of detection, having a thickness T1 which is larger than the width W of the slit S as shown in FIG. 6.
When the thick object 7 of detection is detected with the aforementioned trans-missivetype photo-interruptor, because of the use of only one light emitting element 1, quantity .phi.1 of light incident upon the light receiving element 5a becomes less than quantity .phi.2 of incident light obtained for the thin object of detection (see FIGS. 5 and 6). Accordingly, with the object 7 of detection having the thickness larger than the width of slit S, an outputpeak value M as seen in FIG. 7 is lowered to decrease a ratio M/N and disadvantageously, only an output signal of a small S/N ratio is allowed to be delivered.
As further related art, there are mentioned, for example, Japanese Patent Laid-open No. Hei 1-40970, Japanese Utility Model Laid-open No. Hei 2-44358, Japanese Utility Model Laid-open No. Hei 2-101555 and Japanese Utility Model Laid-open No. Hei 2-114951.